<!DOCTYPE html>
<title id="t"></title>
<script src="../resources/testharness.js"></script>
<script src="../resources/testharnessreport.js"></script>
<script src="spec/resources/custom-elements-helpers.js"></script>
<body id="b">
<script>
test_with_window((w) => {
  class X extends w.HTMLElement {}
  t.appendChild(b);
  // If the following line does not crash, the test passed.
  w.customElements.define('a-a', X);
});
</script>
